The present invention relates to a diaphragm pump having a diaphragm which performs pumping action by changing its form.
FIG. 6 shows the diaphragm pump disclosed in Japanese Laid-Open Utility Model Publication No. 7-14179. A device case 91 of this pump is provided with a block 94 and a pressing plate 98 which is fixed to this block 94. The block 94 and the pressing plate 98 sandwich an outer peripheral portion 92a of a diaphragm 92. The diaphragm 92 and the block 94 define a pump chamber 95.
The above described pump is further provided with a rod 96 and a support member 97. The rod 96 is made to move in a reciprocating manner by a driving source, such as an electric powered motor (not shown). The support member 97 links the rod 96 to the center portion of the above described diaphragm 92. The support member 97 is provided with a first movable member 97a which is placed on the upper surface of the diaphragm 92, as viewed in FIG. 6, and a second movable member 97b which is placed on the lower surface of the diaphragm 92. The first movable member 97a and the second movable member 97b sandwich the center portion of the diaphragm 92.
When the rod 96 moves in a reciprocating manner, the diaphragm 92 changes its form (is displaced), so that the volume in the pump chamber 95 increases or decreases. In case of the suction process, during which the volume in the pump chamber 95 increases, a fluid is sucked into the pump chamber 95. In case of the discharge process, during which the volume in the pump chamber 95 decreases, the fluid is discharged from the pump chamber 95.
Meanwhile, the device case 91 sandwiches the outer peripheral portion 92a of the diaphragm 92, while the support member 97 of the driven body 93 sandwiches the center portion of the diaphragm 92. That is to say, there is constant stress due to the above described sandwiching in the outer peripheral portion 92a and the center portion of the diaphragm 92. As a result, an excessive load is continuously applied to the diaphragm 92, decreasing the durability of the diaphragm 92.